It is sometimes required that an oscillating member be moved in a particular direction. Where this is necessary, use is made of separate moving means to advance the member in that direction. This means is usually heavy, cumbersome and costly. An example of such an oscillating member is an underground percussion drill that requires thrusting. The thrusting is often effected with a drill leg or rig thrust cylinder.
It may also be favourable to convert the oscillation of an oscillating member into movement of a separate member.